NiteRider is updating their lineup so last year's models are going down in price. The MiNewt 600 Cordless (which is being upgraded to a 650 for next year) is everywhere for about $100+ and is very good (as mentioned by K'Tesh). Actual measured lumens is in the high 400s and quality is very high. Click here
http://reviews.mtbr.com/2012-bike-lights-shootout to see some comparisons with it and other lights. I'm using a NiteRider Pro 1500 which is a flamethrower, but it's more than you want to pay . . .